The present invention relates to a method for producing sponge metal, in particular sponge iron, from charging materials consisting of metal ore or iron ore respectively, preferably in lumps and/or pellets, and optionally fluxes, wherein a CO-- and H.sub.2 -containing feedgas from a gas source which is compressed and optionally subjected to CO.sub.2 elimination and heating is supplied to a reduction zone to serve as a reducing gas and after reaction with the metal ore is withdrawn from the reduction zone as an export gas for further use by a consumer. The present invention is also directed to a plant for carrying out the method.
A method of this type is known from AT-B-396.255 and from DE-C-40 37 977. With these known methods, the gas source is formed by a first reduction zone, in which iron ore is directly reduced to sponge iron, wherein the sponge iron is melted in a meltdown gasifying zone under the supply of carbon carriers and oxygen-containing gas and a CO-- and H.sub.2 containing reducing gas is produced which is fed to the first reduction zone, is reacted there and withdrawn as a feedgas for the further reduction zone. According to AT-B-396.255, the feedgas prior to being fed to the further reduction zone is subjected to CO.sub.2 elimination by a reformer and at the same time is heated; in accordance with DE-C-40 37 977, CO.sub.2 elimination is effected by a CO.sub.2 scrubber.
With these known methods, export gas withdrawn from the further reduction zone is subjected to scrubbing and is subsequently mixed with the export gas from the first reduction zone, and the mixed gas thus formed is subjected to CO.sub.2 elimination and heating. This gas mixture is then supplied to the further reduction process to serve as a reducing gas. It thereby becomes feasible to exploit a portion of the reductants still present in the export gas from the further reduction zone, as the export gas is supplied to the further reduction process as a recycle reducing gas.
Often, there is a requirement for the export gas from the further reduction zone to be available for an external consumer, f.i. as a fuel gas. The export gas from the further reduction zone will then not be recycled. In this case, provisions must therefore be made to ensure that a sufficient amount of reducing gas will be available at any time to enable steady operation of the reduction process. In particular, the supply to the further reduction zone of a sufficient amount of reducing gas is to be ensured even with different operating states of the entire plant, f.i. even in the event of a failure.